Oral candidiasis is one of the opportunistic infections commonly associated with AIDS. The overall objective of this work is to understand the relationship between the development of oral candidiasis and pathogenesis of AIDS. The initial study examined by culture the level of oral yeast in a population of HIV-1 antibody positive AIDS patients participating in NIH outpatient protocols with no history of opportunistic infections. Both the patient group and the normal control group consisted of non-smoking, non-denture-wearing males taking no medication. The mean level of yeast in the whole saliva of the AIDS patients was 13,000 colony-forming-units (cfu) per milliliter compared to a mean of less than 1.0 cfu/ml in the control group. Identification of the yeasts showed that Candida albicans was the predominant yeast in both groups. These results indicate that 1) high oral yeast concentration in whole saliva may be an early sequela of HIV-1 infection, 2) high levels of oral yeast precede overt clinical signs of candidiasis, and 3) the oral yeast in these patients results from proliferation of the normal yeast oral flora rather than colonization by unusual species. A second study is underway as part of the protocol entitled "Natural History of Oral Manifestations of HIV-Infection in a United States Military Population." The study population, which may eventually reach 1000 subjects, consists of HIV-1 serum positive army personnel who receive an initial comprehensive examination followed by reevaluations at 6 month intervals. Whole saliva is examined for the presence and level of yeast and total salivary bacterial count. In addition, the presence of Pneumocystis carinii will be ascertained using indirect immuno-fluorescence techniques. The appearance of oral pathogens will be followed in relation to both the stage of HIV infection and the appearance and progression of other clinical symptoms.